Machines for tensioning lengths of textile material are well known in the art for various types of treatment, e.g., drying and fixing of lengths of textile material. A length of material to be treated is conveyed continuously in the longitudinal direction through the tensioning machine with the aid of two suitable, continuously moving conveyor devices (e.g., chains or belts provided with grippers), and its edges are held by the grippers carried on the conveyor devices. For this purpose, each gripper has a gripper flap which can be moved towards the gripper table and can be pivoted between an open position and a closed position. This opening and closing of the gripper flaps is carried out with the aid of appropriate means which are provided at the inlet end and at the outlet end of the tensioning machine. In most of the known tensioning machines, these openers and closers are formed by static arrangements, e.g., by a type of guide bar, which are arranged in the region of the turning ends of each continuously moving conveyor device in such a way that they can be brought into sliding engagement with the gripper flaps or pivot actuating levers connected thereto for the purpose of closing or opening the gripper flaps.
This construction and co-operation of the grippers and the closing and opening arrangements for the gripper flaps can be regarded as fairly satisfactory so long as the conveyor devices move at relatively low speed. However, in the more modern constructions of tensioning machines, higher operating and conveying speeds (up to 300 m/min and more) are increasingly aimed for. These high speeds lead to an extremely rapid wear of the closing and opening arrangements on the one hand and the grippers on the other hand, in particular the gripper flaps which are in frictional engagement with these arrangements, so that the advantage of the high operating speeds is cancelled out by undesirable shut-down periods and by particularly high repair and maintenance costs, that is to say by quite considerable disadvantages.
The object of the invention, therefore, is to improve a tensioning machine of the type referred to, particularly in the region of co-operation between the grippers and the closing and opening arrangements for the gripper flaps, in such a way that even at very high operating and conveying speeds the wear on the closing and opening elements and on the gripper flaps is largely eliminated or reduced to a minimum and at the same time, even at these speeds, a reliable closing and opening function is ensured.